The present invention relates to air scrubber systems in general, and in particular, to a multi-stage, modular air scrubber system which can be custom tailored to effectively handle many air treatment applications.
Currently, air scrubber systems must be built from the ground up according to specifications for each job. Except for the obvious utilization of various common items of hardware, such as valves, pumps, filters and the like, there is no presently available air scrubber system which includes substantially complete modules which can be connected or disconnected to increase or decrease the scrubbing capacity of the system with minimal plumbing and hardware changes. As a result, modifications and/or change over from one job application to the other are often costly and time consuming.
It is therefore one object of the invention to provide a relatively simple and inexpensive modular design for multi-stage air scrubber units, facilitating addition and reduction of scrubber capacity, as well as changeover to other treatments with minimal expenditure of time and effort.
In one exemplary embodiment of this invention, the air scrubber system comprises at least three scrubbing modules or towers configured to remove hydrogen sulfide through counter current contact of contaminated air with an aqueous, alkaline scrubbing solution. Each scrubbing tower includes a substantially L-shaped housing, formed with an upper portion which includes a column packed with contact media, and a lower portion which includes liquid sump containing a scrubbing solution.
A liquid recirculation system is provided for each module which comprises a continuously operating submersible pump located in the lower portion of the tower, appropriate plumbing, and a spray discharge head comprising a plurality of nozzles for discharging scrubbing solution onto the contact media in the upper portion of the tower.
Access to the packed column is provided by way of a sealing lid mounted atop the scrubber unit, while access to the liquid sump section is provided by way of a removable cover located directly above the sump.
In one exemplary embodiment, where the modules are arranged for counterflow scrubbing of air, an air inlet is provided in the first of three modules, for supplying air from a wet well to the lower portion of the first module, but above the level of scrubbing solution. Apertures are also provided in the upper portions of adjacent, facing side walls of the modules which permits air to flow from the first to third modules in succession. The second and third modules are provided with partitions in their respective upper portions which create flow paths for the air between the upper and lower portions of these modules. The third module is also provided with an air outlet in its upper portion, leading to an outlet duct, air blower and exhaust stack.
In this same exemplary embodiment, a scrubber solution inlet is provided in the lower portion of the third inlet, and spillways are formed in the adjacent, facing walls of the lower portions of the second and third modules, while a scrubber solution drain is provided in the lower portion of the first module. Because the scrubber solution inlet, spillways and drain are at successively lower heights in the respective module walls, the scrubber solution passes through the system in a direction opposite the air flow direction.
The air scrubber system in accordance with one exemplary embodiment of the invention also provides for intimate mixing of water and a suitable alkaline chemical, for example, to form an aqueous scrubbing solution prior to introduction of the solution into the appropriate scrubber module. The system also provides for delivery of the aqueous scrubbing solution to the scrubber towers at a predetermined rate, adjustable within predetermined limits, in conventional fashion. Both air scrubber solution feed and chemical feed controls are preferably housed in an accessible control panel located proximate to the modules. Spent scrubbing solution is disposed of via a sewage system which forms no part of this invention per se.
In operating the air scrubber system in accordance with the exemplary embodiment, contaminated air to be treated is conveyed from a source successively through the three air scrubber towers with the aid of the blower at the outlet side of the system, where cleaned air is discharged to atmosphere via the stack. More specifically, the air is constrained to flow upwardly through the contact media of the first module, downwardly through the passageway formed in the second module adjacent the contact media to the lower portion, then upwardly through the contact media in the second module. After similar flow through the third module, the air is drawn into the outlet duct and exhausted to atmosphere.
At the same time, scrubbing solution is passed successively through the towers in the opposite direction, i.e., in a counterflow arrangement. Specifically, scrubbing solution is fed into the lower portion of the third module, spilling over into the second and first modules. Simultaneously, solution is pumped from the lower portion of each module up into the upper portion of the respective modules to be distributed across the contact media via the spray head discharge nozzles. Cleansing of the air in this exemplary embodiment occurs within the upper portion of each tower as the air flows upwardly through the contact media while scrubbing solution flows downwardly through the contact media.
In another aspect of the invention, an additional smaller contact media column is provided above the spray head assembly, in the third, or outlet module to provide demisting of the air prior to discharge to atmosphere.
Since each of the scrubbing towers is essentially identical in construction, addition or subtraction of individual towers, for increasing or decreasing scrubbing capacity, is easily accomplished.
In addition, the flow paths may be reversed or altered inlets and outlets may be changed, and contact media size and composition may be altered in accordance with job requirements with minimal effort. In addition, one or more types of scrubbing solutions or treatment fluids may be utilized, e.g., caustic or hypochlorite solution, either alone or in combination, depending on the process. In this regard, it is possible to have different treatment fluids in the same or in adjacent units. Thus, the same modules may be utilized in any number of air treatment processes, providing a degree of versatility and flexibility heretofore unavailable in the art.
Other objects and advantages will become apparent from the detailed description which follows.